Front-end loaders, which in common versions are known also as skid-steer loaders, are exemplified in Melroe et al. U.S. Pat. No. 3,231,117. Such loaders are used with various implements including dirt buckets, grain buckets, and manure forks, and are used commonly on farms or construction sites or in other harsh environments.
Typically, such a loader has, at its front end, lifting and tilting means, such as a pair of hydraulically operated load-lifting arms, which are journalled at their distal ends to a male coupling structure, and a pair of hydraulically operated load-tilting pistons, which also are journalled at their distal ends to the male coupling structure.
Typically, each implement for such a loader is provided with a female coupling structure, which is welded integrally to such implement. The male coupling structure is adapted to be selectively coupled to and uncoupled from the female coupling structure. When the male coupling structure is coupled to the female coupling structure, the implement may be selectively lifted and lowered, by means of the load-lifting arms, and may be selectively tilted, by means of the load-tilting pistons. It is known to employ hydraulically or manually actuated pins, wedges, or similar components to latch the male coupling structure releasably to the female coupling structure.
Various examples of such coupling structures, as known heretofore, are disclosed in Lane U.S. Pat. No. 3,204,793, Wallberg U.S. Pat. No. 3,269,570, Bauer et al. U.S. Pat. No. 3,672,521, Cochran et al. U.S. Pat. 4,545,720, and Kewacos Norwegian Patent No. 91,351. Other known structures of related interest are disclosed in Przybylski U.S. Pat. No. 2,963,183, Pilch U.S. Pat. No. 3,220,487, Bauer U.S. Pat. No. 3,732,996, Clevenger et al. U.S. Pat. No. 3,794,195, and Steelfab British Patent Specification No. 975,029.
In a typical arrangement, the female coupling structure comprises an upstanding back plate, which may be an integral part of the implement or a plate welded to the implement, an upper flange extending rigidly from the back plate and sloping downwardly and backwardly, and a lower flange extending rigidly and backwardly from the back plate, and the male coupling structure comprises an upstanding front plate, which may have an upper flange extending rigidly from an upper edge of the front plate and sloping upwardly and frontwardly, and paired brackets, which are used to mount the male coupling structure operatively to the lifting and tilting means of the material-handling apparatus. In such an arrangement, the male and female coupling structures respectively have welded steel parts.
In such an arrangement, the upper flange on the front plate of the male coupling structure or the upper edge of that plate, if such a flange is not used, is adapted to bear against the upper flange of the female coupling structure when the male coupling structure is being coupled to or uncoupled from the female coupling structure, and while the male coupling structure remains coupled to the female coupling structure. Conventional manufacturing tolerances for welded structures such as these leave a gap or space between the male and female coupling structures, as between the front plate of the male coupling structure and the back plate of the female coupling structure, when the upper flange of the front plate of the male coupler structure or the upper edge of that plate, if such a flange is not used, bears against the upper flange of the female coupling structure. The Bauer et al. patent noted above discloses, in specific reference to FIG. 12 of that patent, a gap or space between the front plate of the male coupling structure and the back plate of the female coupling structure, as an intended feature.
If the gap or space therebetween is too small, interference between adjacent parts of the male coupling structure and the female coupling structure may hamper or prevent proper coupling and uncoupling action. If the gap or space therebetween is too large, vertical play between the male coupling structure and the female coupling structure may permit excessive distortion, particularly under heavy loads, and may permit the implement to fall off the material-handling apparatus. Moreover, if the gap or space therebetween is too large, the aforementioned pins, wedges, or similar components may not be fully engaged in their receptacles when the male and female coupling structures are coupled to each other, whereby the implement may tend to fall off the material-handling apparatus.
There has been a need, therefore, to control any gap or space between the male and female coupling structures within precise limits and yet to employ conventional manufacturing tolerances for welded parts of the implement-coupling assembly.
Hereinabove, and hereinbelow, directional terms such as "front", "back", "frontwardly", "backwardly", "upper", and "lower", are used merely for convenience reference to relative positions of different parts and to relative directions and not intended as limiting.